<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var num1 = 1;
    var num2 = 1;
    for(i = 3; i<=12; i++) {
        num2 = num1 + num2;
        num1 = num2 - num1;
    }
    alert(num2);
</script>
</body>
</html>